IE56681B1 - Prosthetic implant for a metatarso-phalangeal articulation and a cutting device for positioning same - Google Patents

Description

For some twenty years the problem of the prosthetic or nonprosthetic reconstitution of metatarsophalangeal joints has been discussed, no matter whether these involve arthrosis or an unsuccessful surgical resection of the head of the first metatarsal. The first solution adopted was the screwed autograft, but in 100¾ of cases the graft lysed.

Since 1969, various prosthetic implants have been envisaged: Silastic implant.

Either of the phalangeal only type, but involving lysis of the diaphysis or wear to the head of the metatarsal bone; or of the hinge type, but wearing the fracturing occur with lysis of the adjacent bone, so that there is a considerable bone deficit after 3 to 4 years representing between 20 and 30¾ of the local bone volume. 2. Cemented Teflon-metal prosthesis in two parts, Teflon being a registered trademark for fluorocarbon resins. There is a bone lysis in contact with the prosthetic elements. Bone lyses are often prot>lemmatical to repair. 3. Thus, bone lysis occurs both with the screwed autograft and the prosthetic implant. It is logical to think that this phenomenon is directly associated with the extent of the stresses occurring at the first metatarsophalangeal joint, which led to the idea of the Docteur Regnauld Teflon prosthesis. This prosthesis is only in the form of a thin cupula with no bone engagement. As it is only 1 mm thick, it does not give rise to stresses and if it has to be removed its small overall dimensions means that there is no regional deficit. However, the absence of bone fixture leads to a frequent partial migration out of the effectiveness zone.

US-A-4 231 121 describes metacarpal and phalangeal prostheses maintained in place by driving a rod into the medullary canal of the corresponding bone, which progressively brings about a significant bone lysis. In this document, the phalangeal prosthesis has an outer concave surface and the metatarsal bone an outer convex surface of the same curvature as that of the concave surface.

In order to obviate these disadvantages (lysis or migration), the present invention is directed at a small prosthetic Implant, i.e. only receiving limited stresses, but which is adequately fixed to the bone to ensure that no migration takes place.

This implant comprises a phalangeal prosthesis having a concave outer surface and a metatarsal prosthesis having a convex outer surface of the same curvature as that of the concave surface, characterized in that the phalangeal prosthesis (1) is in the form of a cupula having a hollow cylindrical part (2) connected to a base (3), whose outer face (4) is concave in order to fulfil the function of the articular cartilage which has disappeared, said cupula serving to cover the bottom of the first phalanx (8) of the toe to be treated by hard frictional driving in of its cylindrical part into the recesses with corresponding dimensions formed by means of a trephine in the corticalis, namely the osteophytes (9) surrounding said bottom of the first phalanx, the cupula (1) thus being fixed in the bone by a portion of its cylindrical part (2) and in that the metatarsal prosthesis (5) comprises a part shaped like a spherical cap (6) which will serve as the articular cartilage and which surmounts a part shaped like a truncated cylinder (7) to which it is connected, • 30 said metatarsal prosthesis serving to be fixed to the anterodorsal face of the head (10) of the metatarsal bone (11) corresponding to said (ne by said truncated cylinder (7), which for this purpose is driven in with hard friction and is thus locked in a recess having corresponding dimensions and formed by means of a trephine in the dorsal region of the head of said metatarsal bone. 0 For better fixing purposes, the metatarsal prosthesis has a spindle with a striated contour arranged substantially centrally perpendicular to the base of the prosthesis.

The prostheses can be made from a fluorocarbon resin, such as the known under the registered trademark Teflon, which is well supported by the organism, or can be in the form of carbon fibres (which are integrated with the bone), or can even be made from a metal accepted by the organism, such as stainless steel or a cobalt-molybdenum-chromium alloy, e.g. that known under the registered trademark Vitallium. The metatarsal prosthesis is preferably metallic.

Thus, the present implant comprises two prostheses, which are not sealed and are instead simply wedged or jammed in the bone by hard friction. In addition, they are neither heavy, nor voluminous. The thickness of their walls in approximately 1 mm, except that of the planoconcave base of said cupula, which varies from 0.5 to 1 mm in the centre to 2 to 3 mm on the periphery.

The cylindrical part of the cupula covers the metaphysis or the distal part of the diaphysis of the first phalanx, a function of whether it has been decided to shorten the latter during the operation. The cupula is inserted along the axis of the first phalanx until its bottom strikes against the latter. - 5 The metatarsal prosthesis is indispensable when the articular cartilage of the head of the metatarsal bone is severely deteriorated. In this case, it is important to only resect a very limited amount of said head and only in its anterodorsal region. Thus, it is necessary to avoid stress which would lead to the melting of the bone on the plantar face of said 6 head, which bears on the ground when walking. Therefore the insertion axis of the metatarsal prosthesis is deflected upwards with respect to the axis of the metatarsal bone, e.g. by 45°. This angle is favourable, because the basic movements of the metatarsophalangeal joint take place on either side of this 45° axis. With this position of the metatarsal prosthesis, the two functions of the metatarsal head are maintained in an optimum manner.

Thus, the osseous structure on its lower face continues to support the weight of the body, whilst the prosthesis on its upper face permits the conventional mobility of the joint.

The invention also relates to a drilling tool for the position of a prosthetic implant, such as the aforementioned interposed cupula.

Hitherto, in bone surgery use has mainly been made of spherical cap-shaped implants. Such implants, also called interposed cupulas, are provided on their periphery with holes permitting their fixing to part of the bone to be repaired, which has previously been appropriately cut. These spherical cap-shaped cupulas suffer from the disadvantage of skidding and consequently fail to give a reliable osteosynthesis.

A new process has now been discovered from positioning the * prosthetic implant. This process consists of making on the end of one of the two bones of the articular region to be repaired, a cylindrical projection using a drilling device, * depositing on said cylindrical projection of the bone a cupula - 6 having a corresponding cylindrical recess and a curved face for coming into contact with a prosthesis on the facing end of the other bone of said articular region and putting said other bone back into place. This process is particularly suitable for repairing joints of the ball and socket type and in particular the joints of the feet.

The drilling device used comprises a rot (25) provided at one of its ends with a grip (26) and having at its other end a tubular drill (30) constituted by a tube having on one of its edges a series of teeth (31) intended for cutting purposes, characterized in that it also comprises an inner central drill (27) fixed to the rod (25) and constituted by a solid cylinder (28) placed within the tubular drill (30) and connected to the latter and having on its end face a series of radially extending teeth (29), as well as optionally a central bit (32) mounted in the inner central drill (27) and fixed in said rod (25).

Embodiments of the prosthetic implant according to the invention and the drilling device used for the positioning thereof will now be described in greater detail in nonlimitative manner with reference to the attached drawings, wherein show: Figs. 1a, 1b and 1c respectively a plan view, an elevation and an axial vertical sectional view of the phalangeal prosthesis of a prosthetic implant of the metarsophalangeal joint of the big toe.

Figs. 2a, 2b and 2c respectively a plan view, an elevation and an axial vertical sectional view of the metatarsal prosthesis of said implant.

Fig. 3 a diagrammatic elevation showing the prosthetic implant fitted in the region of the metatarsophalangeal - 7 joint of the big toe, the tissues of the foot being removed.

Fig. 4 a sectional view along line IV-IV of fig. 3.

Fig. 5 an elevation and sectional view of the drilling 5 device according to the invention and the bone after drilling.

Fig. 6 an end view of the drilling device according to fig. 5.

Figs. 7 and 8 constructional variants of the inner central drill.

The phalangeal prosthesis (figs. 1a 1b and 1c) is a cupula 1, e.g. moulded from Telfon, which comprises a cylindrical part 2 connected to a base 3, whose outer face 4 is concave. The cylindrical part 2 is hollow.

The metatarsal prosthesis 5 (figs. 2a 2b and 2c) comprises a spherical cap-shaped part 6 surmounting a part shaped like a truncated cylinder 7 to which it is connected. The inner surface of said cylinder is striated. The metatarsal prosthesis can be produced by moulding Telfon, but is preferably metallic.

The phalangeal prosthesis 1 has a diameter approximately corresponding to that of the bottom of the first phalanx 8 of the big toe, the osteophytes surrounding said bottom region being removed. In order to permit the fitting of said prosthesis, use is made of a trephine, whose internal and external diameters correspond to those of the cupula 1. Using said trephine, hollowing out takes place parallel fo the direction of the axis of the first phalanx 8 of recesses in the corticalis and in the osteophytes 9 located around the base of the phalanx. The length of these recesses must be equal to that of the cylindrical part 2 of the cupula. The latter is then driven with hard friction into said recesses via its cylindrical part 2, whose thickness is equal to that of the recesses, until the inner face of the base 3 of the cupula comes into contact with the end face of the first phalanx 8 (Fig. 3). It can be seen in fig. 4 that the cupula 1 covering the base of the first phalanx 8 is only inserted and fixed in the bone in the region of the osteophytes 9, i.e. by only a fraction of its cylindrical part 2.

The metatarsal prosthesis 5 is put into place on the anterodorsal face of the head 10 of the first metatarsal bone 11. it is driven into said head via its part shaped like a truncated cylinder 17 along an axis which is e.g. upwardly deflected by 30 to 45° with respect to the axis of the first metatarsal bone. As in the case of the phalangeal prosthesis, a recess permitting driving in under hard friction is prepared by means of a trephine having internal and external diameters corresponding to those of the part shaped like a truncated cylinder 7. Insertion takes place until the part shaped like a spherical cap 6 is in contact with the head 10 of the first metatarsal bone 11. The plantar face 12 of the head remains free.

The curvatures of the concave base 4 of cupula 1 and the spherical cap 6 of the metatarsal prosthesis are identical in order to permit an appropriate relative pivoting.

In Fig. 3, the bones are diagrammatically shown in mixed line form and the phalanx 8 is clearly separated from the first metatarsal bone 11 in order to show the prostheses with a greater degree of clarity.

In order to consolidate its fixing, the metatarsal prosthesis 5 preferably has a spindle with a striated contour 13 shown in - 9 fig. 2c and positioned centrally substantially perpendicular to the truncated cylinder-shaped base 7 of the prosthesis. A locking loop 14 (fig. 1c) made from steel wire can reinforce the fixing of the phalangeal prosthesis, which it traverses diametrically and whose ends are engaged on the lateral surface of the prosthesis.

As shown in fig. 5, the process can consist of producting a cylindrical projection 21 on one end of the bone 22 to be repaired, placing on said projection 21 a cupula 1 having a cylindrical recess 2 corresponding to said projection and a concave outer curved face 4 for coming into contact with a metatarsal prosthesis 5 placed on the end of the other bone. The osseous cylindrical projection 21 is produced with the aid of the drilling device shown in figs. 5 and 6. This drilling device is constituted by a rod 25 provided at one of its ends with a grip 26 and at the other end with the actual drilling means, which comprise: 1) An internal central drilling 27 constituted by a solid cylinder 28 having on its end face a series of teeth 29 extending radially on said end face, the cylinder being recessed in its axial part, the recess 18 being such that it permits the fixing of the cylinder on rod 25. 2) A tubular drill 30 constituted by a tube fixed to the central drill 27, e.g. by means of a screw 15 engaged in a taphole 16 of the cylinder 28 of the internal central drill, the tube 30 having on one of its edges a series of cutting teeth 31.

The central drill 27 can also have an axial hole in which is « fixed a central bit 32. The teeth 31 of the tubular drill 30 and those 29 of the internal central drill are directed from the same side. The teeth of the two drills are either in * sawtooth form, or have cut faces.

By rotating the drilling device, centered with the aid of the bit 32 on the part 22 to be treated, a projection is formed, whose height varies as a function of the distance separating the teeth of the tubular drill 30 from those of the internal central drill 27. The latter can be positioned with a varying depth in the tubular drill 30. When the teeth have cut faces, the rotation must be in alternating form.

As a result of the internal central drill 27, the upper part 33 of the bone projection 21 is appropriately levelled to give a planar surface, which is convex or concave, as a function of whether the teeth of the internal central drill 27 are in one plane or are arranged in such a way as to define by rotation a convex or concave surface, as shown in figs. 7 and 8, the dotted line therein representing the shape of the corresponding projections obtained with the concave or convex internal drills.

The end of the wall of the cylindrical body can be cut along a plane parallel to the inner face of the bottom of said body or along an oblique plane.

The cupula can be made from any random material presently used in bone surgery, such as e.g. metal, plastic, carbon, bone, medical ceramic, etc.

The drilling device according to the invention is made from stainless steel or any other metal or alloy, e.g. titanium, chromium-cobalt, carbon, etc.

Technical equivalents are possible to the prosthetic implant and to the drilling device described hereinbefore without passing outside the scope of the invention.

Claims (5)

1. Prosthetic implant for a phalangeal prosthesis having a concave outer surface and a metatarsal prosthesis having a convex outer surface of the same curvature as that of the 5 concave surface, characterized in that the phalangeal prosthesis is in the form of a cupula having a hollow cylindrical part connected to a base, whose outer face is concave in order to fulfil the function of the articular cartilage which has disappeared, said cupula serving to cover 10 the bottom of the first phalanx of the toe fo be treated by hard frictional driving in of its cylindrical part into the recesses with corresponding dimensions formed by means of a trephine in the corticalis, namely the osteophytes surrounding said bottom of the first phalanx, the cupula thus being fixed 15 in the bone by a portion of its cylindrical part and in that the metatarsal prosthesis comprises a part shaped like a spherical cap which will serve as the articular cartilage and which surmounts a part shaped like a truncated cylinder to which it is connected, said metatarsal prosthesis serving to 20 be fixed to the anterodorsal face of the head of the metatarsal bone corresponding to said toe by said truncated cylinder, which for this purpose is driven in with hard friction and is thus locked in a recess having corresponding dimensions and formed by means of a trephine in the dorsal 25 region of the head of said metatarsal bone.

2. Prosthetic implant according to claim 1, characterized in that the part shaped like a truncated cylinder of the metatarsal prosthesis is internally striated.

3. Prosthetic implant according to claims 1 or 2, 30 characterized in that the phalangeal prosthesis and the metatarsal prosthesis are made from fluorocarbon resins, carbon fibres or a metal accepted by the organism.

4. Prosthetic implant according to claim 3, characterized in that the metatarsal prosthesis is metallic. 5. Prosthetic implant according to any one of the claims 1 to 4, characterized in that at least one steel wire locking loop is associated with the phalangeal prosthesis. 6. Prosthetic implant according to any one of the claims 1 to 5, characterized in that the metatarsal prosthesis has a fixing spindle with a striated contour arranged centrally and substantially perpendicular to the base of the prosthesis. 7. Drilling device for bone surgery and in particular for fitting the prosthetic implant according to claim 1, comprising a rod provided at one of its ends with a grip and having at its other end a tubular drill constituted by a tube having on one of its edges a series of teeth intended for cutting purposes, characterized in that it also comprises an inner central drill fixed on the rod and constituted by a solid cylinder placed within the tubular drill and connected to the latter and having on its end face a series of radially extending teeth, as well as optionally a central bit mounted in the inner central drill and fixed in said rod. I I 8. Device according to claim 7, characterized in that the teeth of the tubular drill and those of the internal central drill are directed from the same side. / 9. Device according to either of the claims 7 and 8, characterized in that the teeth of the two drills are sawtooth or have cut faces. 10. Device according to any one of the claims 7 to 9, characterized in that the tubular drill is mounted on the internal central drill by means of a screw engaged in a taphole of the cylinder of the internal central drill, said internal drill being positioned with a varying depth in the tubular drill. 11. A prosthetic implant substantially as hereinbefore described with reference to the accompanying drawings.

5. 12. a drilling device substantially as hereinbefore described with reference to the accompanying drawings.